1. Field of the Invention
The present invention relates to a lamp for an automobile.
2. Description of the Related Art
Conventional lamps for automobiles include lamps disclosed in U.S. Pat. Nos. 6,232,707 and 6,056,417. The lamps for automobiles in each of these patents have substantially the same configuration, and therefore the lamp for an automobile disclosed in U.S. Pat. No. 6,056,417 will hereinafter be described as a typical example.
FIG. 10 is a perspective view of a lamp for an automobile disclosed in U.S. Pat. No. 6,056,417. As shown in the figure, this lamp includes a lamp 110, and a base portion 130 to which the lamp 110 is mounted.
The lamp 110 is designed such that pairs of lead wires 11 mounted to both ends of filaments 12 are charged with electricity to cause a current to flow through the filaments 12 to thereby emit light due to electrical resistance of the filaments 12. The filaments 12 are disposed within a generally spherical glass envelope 21 of a bulb 20, and an inactive gas is enclosed in the glass envelope 21. Intermediate portions of the lead wires 11 are fixed by a pinch seal portion 22 of the bulb 20, and the lead wires 11 extend downwardly from the pinch seal portion 22. An exhaust tube 13 is sealed at a central portion of the pinch seal portion 22. This exhaust tube 13 is a tube used to establish an inactive gas atmosphere in the glass envelope 21 and after establishing the inactive gas atmosphere, is subjected to melt sealing to close the tube.
The base portion 130 includes a resin adapter 140 and a fixing member 150.
The resin adapter 140 includes a lamp mounting portion 141 for mounting the pinch seal portion 22 of the lamp 110, and a portion 142 which forms a base cap when lead wires are folded around its external surface, with a fitting cavity 143 being formed vertically therein. The fitting cavity 143 is fitted with the pinch seal portion 22 of the lamp 110 to thereby allow the lamp 110 to be mounted in the resin adapter 140.
When the lamp 110 is mounted in the resin adapter 140, portions of the lead wires 11 extending downwardly from a lower end of the portion 142 are bent or folded upwardly so that the folded portions of the lead wires 11 extend along a lower surface of the resin adapter 140. These folded portions of the lead wires 11 become a base cap through which a current is supplied from the outside.
Peripheral portions of the portion 142 of the resin adapter 140 are fitted with the fixing member 150 to fix the folded portions of the lead wires 11 in order to prevent the folded portions from being shifted from the proper positions.
The lamp 110 is manufactured in accordance with the following procedure before being mounted in the resin adapter 140.
First of all, the lead wires 11 of the lamp 110 are folded outwardly at a position lower than that of the lower end of the pinch seal portion 22. Folding the lead wires 11 makes it possible to prevent the lead wires from being melted or burned in the later melt sealing procedure. Next, the inactive gas atmosphere is established inside the lamp 110 through the exhaust tube 13, and an opening portion of the exhaust tube 13 is then subjected to the melt sealing procedure for heating and melting of the opening portion. Finally, the folded lead wires 11 are unfolded and restored into the original straight wires.
The lamp 110 having the lead wires 11 unfolded into the original straight wires is mounted in the resin adapter 140 to thereby assemble the lamp for an automobile.
However, the conventional lamp for an automobile has the following problems (i) to (iii).
(i) Since the lead wires 11 are unfolded for restored into the original straight wires after being firstly folded, the unfolding of the lead wires 11 is insufficient in some cases. In a case where the unfolding of the lead wires 11 is insufficient, there is a fear that the lead wires 11 are bent during insertion of the lead wires 11 into fine insertion holes 141 of the resin adapter 140, and in the worst case, the lead wires 11 can not be inserted into the insertion holes 141 of the base portion 140.
(ii) The positions of the filaments 12 inside the lamp are defined by a distance from a reference surface using an upper end of the resin adapter 140 in the base portion 130 as a reference surface. If the filaments are shifted from their proper positions, then an adverse influence is exerted on an illuminating angle. However, in the conventional lamp for an automobile, when the lamp 110 is mounted in the resin adapter 140, the lamp is continued to be inserted into the insertion cavity 143 of the resin adapter 140 until an upper end of the resin adapter 140 comes in contact with the glass envelope 21 of the bulb 20 in order to be positioned. For this reason, if processing accuracy for the glass envelope 21 of the bulb 20 is poor, then a position shift occurs in the reference surface, the positions of the filaments 12 are shifted accordingly, and hence the lamp concerned becomes a defective product.
(iii) A distal end side of the folded portions of each of the lead wires is held between the fixing member 150 and the resin adapter 140, whereby the lamp 110 is fixed to the resin adapter 140. In other words, the lamp 110 is merely fixed to the resin adapter 140 only by fixed portions of the lead wires 11. Hence, a firm fixing means is not provided against a vertical position shift. As a result, the filaments 12 may be shifted from their proper positions, or the lamp 110 may move vertically in some cases.